question #3 Sahih Muslim 1130b, Book 13, Hadith 163 : What can be learned from the Prophet’s inquiry about the fasting practices of other religious communities?

This hadith has been narrated by Ibn Bishr with the same chain of transmitters (but with a slight variation) that he (the Holy Prophet) inquired of them (Jews) about it (fasting on the day of ‘Ashura).